A lithium ion capacitor of small size and light weight, having high energy density and capable to discharge and charge repeatedly, has been increased in demand rapidly with using its property. Also, the lithium ion capacitor is expected to utilize from a small size usage such as a cellar phone and a laptop computer to large size usage as adapted for a car because of its high energy density and power density. Therefore, further improvement such as lower resistance, high capacity, high electric strength, improving mechanical characteristic and the like is required to the lithium ion capacitor, according to enlargement of use purposes and development.
The lithium ion capacitor comprises a polarizable electrode at a positive electrode, a non-polarizable electrode at a negative electrode, operating voltage is raised by using an organic electrolyte solution, and an energy density can be improved. However, on the other hand, there were problems that a contact resistance of a collector, having openings which penetrate onside to other side, and electrode composition layer is larger so that an internal resistance is larger.
Hence, in order for decreasing the internal resistance, it has been suggested for coating a conductive paint on a surface of the collector (Patent Document 1). An electrode for lithium ion capacitor in the patent document 1 is obtained by coating a conductive paint on a collector having through holes, and coating slurry for electrode composition layer composed of electrode active material, conducting material and binder thereon. However, for this electrode, the decreasing the internal resistance was insufficient.